Arc-welding generator



Dec. 13, 1927.-

w w 5 a 2 8 H1 M 5 O 6 B M J 9 1 .L m. W 5 1 w H :M AN 3 Filed May 24, 1923 S HANCOCK ARC WELDING GENERATOR Load lqmp.

INVENTOR Staff Hancock WITNESSES:

ATTORNEY '45 explanatorlatentedfDec, id, 1927 ll at T A T ES ears Y scour nsucocn, or WILKINSBURG, rnuusv vaum; ASSIGNOR ro wnsrruonouss nancrnrc a iraivuracrusr ve COMPANY, e. oonronarrou or :enunsynvanm.

ABC-WELDING GENEBATQR,

Application filed May 24,' 1923. Serial 1%. ensue.

My invention relates to dynamo-electric machines and it'has particular relation to direct-current generators which are adapted for use in connection with arc welding syso toms or loads of a similar nature.

The requirements of? a welding generator are well known. The Inc-load voltage of the generator should be approximately 60; to 80 volts. Upon striking the arc, the weldmg to current should remain practically constant over a large range of voltages. The" voltage of the arc varies to a certain extent with the arc len th'and is-zerofat the moment. when the we ding electrodes are short circuited.

lit is essential that,' upon opening the short circuit, the voltage across the electrodes shall be quickly established in'order. that the arc maybe stable. l'term the latterrequirement the speed of action. of the generator and it as is this characteristic which distinguishes successiul arc weldin'g-generators.

' 1 In orderto obtain the speed of action, it is essential that the current in the field winding, supplying the main generator field,

shallnot die down at the moment of the short circuit-oi the electrodes, thereby eliminating the time element required in order to build up the current in the exciting winding of the generator upon opening of the short to circuit, To this end, in previously proposed generators of the above-mentioned. type, the excitation of the generators has been derived either from; an external. independent source or voltage or by thep set of poles in one machine. v

The object of my invention is to provide a self-excited direct current generator of a simple and economical construction having an inherent regulation, essential to a welding 60 are oranother load of a similar character.-

' My inventionwill be best understood from the accompanying drawings, whereinv Figs. l and 2 are 'd1a'grammatic views of two em,- bodiments of my invention and-Fig. 3 is an inaiter. in Fig. 1 is shown an armature 1 co-operatingjwith two pole pieces 2. The armature .is provided with a winding?) and a commu- 50 tator 4. Main-brushes 5 and 5 co-operate with the'commutator 3 and are connected to electrodes 6 constituting the terminals of an arc drawn. between the electrodes.- auxiliary brush 7 is arranged between -the main brushes 5 and 5 and is connected to one rovision of a double.

y curve diagram referred to here- The direction of flow of the current in the armature winding 3 and in the field winding 8 is illustrated by means of dots and crosses, indicating respectively that the current is flowing toward and from the observer With the armature driven in the direction indicated by the arrow ll and with no load connected to the brushes the magnetic flux through the machine will have a direction indicated by the lines 12 and 13. Upon connecting a load to the brushes the current flowing through the armature will set up a flux in the direction indicated by the arrows 14. The flux induced by the armature current will counteract the flux induced by the main winding 8 under the leading portions 15 of the pole pieces Q and will act in the direction of the main flux under the trailing portions 16 of the pole pieces 2, o

The pole pieces 2 are normally saturated and accordingly the augmenting efi'ect of the armature react1on under the trailing portion 16' of the pole pieces will be inappreciable and this portion of the field will remain practically constant, independently of the armature reaction. On the other hand, the opposing effect of the armature reaction under the leading pole side 15 will decrease the flux density in this part of the poles and decrease thereby the total flux through the armature without an appreciable change in the flux density in the trailing portion 16 of the poles.

Under the above conditions the voltage in duced between the main brushes 5 and 5 will tend to decrease with an increase in the armature current, while maintaining practically unchanged voltageconditions inthe 'eportion of the winding connected between "the auxiliary brush 7 and the main brush 5 As the field winding 8 is connected to these 100 brushes 7 and 5*, the exciting current is maintained substantially constant during all conditions of load.- Such arrangement will have a similar eifect as if the field winding 8 were excited from a separate external source. 105 When the arc is short circuited by momentarily touching the electrodes, the voltage across the mam brushes momentarily falls to a very low value. However, the voltage between the main brush 5- and the auxiliary 110 winding 17 is connected in such direction brush 7 remainssubstantially constant, or else falls off but slightly, depending upon the saturation and leakage conditions of the machine and the osition or setting of the auxiliary brush. wing to the fact that the current in the exciting winding 8 does not fall with the 'voltage across the main brushes the resistance 9 connected in the exciting circuit, or by shifting the auxiliary brush -7 or the mam brushes 5 and 5.

In Fi 2 is shown a generator slm lar to that llustrated in Fig. 1, but an addi-.

tional series winding 17 is provided upon the pole pieces to amplif the action of the armature current in re ucing the voltage across the terminals of the are 6 with an in,- crease in the welding current. The series as to give a magneto-motive force which opposes the magnetomotive force of the cur-- rent in the main'exciting winding 8. I In the generator illustrated in Fig. 2, the

saturation in the trailing portion of the pole pieces 2 is increased through the provision of a notch 18 providing a path of narrow cross-section in one portion of each pole piece. This or another arrangement of the same character increases the effectivenessof the machine. v r

In operatlon an increase in theload current increases rapld the series field winding 17 so-that a slight I ingcurrents, the different currents being members with a relatlve y small total increase in the load current is accompanied by a very sharp decline in the load voltage.-

by reason, however, of the s cial construction of the pole members 2 w ich causes saturation of the trailing ortion of the ole the augmenting action of the armature currents is sufiicient to maintain the flux' in that part of the pole members substantially constant independently of the load current.

Fig. 3 s ows the volt-ampere characterisobtained by' a' variation in the resistance win 8.

one 0 ly the demagnetizing'efiect of LBEBJBB rangements herein shown and described but seek to cover, in the appended claims, all

scope of my invention.

Iclaim as my invention: y 1. A direct-current,generator having a field structure comprism alternate north and south salient pole pieces so l'arranged that the trailing portions of the pole .faces. Q

are saturated by reason of the flux distor-x tion'produced by armature reaction, where as the remaining portions of the pole faces are not saturated, main ositive and negative brushes disposed bet een pairs of pole pieces; an auxiliary brush disposed under between the saturated trailing portion and the unsaturated remainder. of the'pole face, and a field windin energized fromsaid auxiliary brush andt e main brush adjacent to said saturated tr' iling portion.

2. A dil'GCt-Cllfl'lt generator having a field structure com rising alternate north and south main sa ient pole pieces .so arranged that the trailing 'portionsof the pole faces are saturated by reason of the flux distortion produced by armature reaction, whereas the remaining portions of, the pole faces are not saturated, main positive and. i

ne .ative, brushes dis sed between pairs .of

o e 'pieces, an auxiliary brush disposed un-f .1

er one of the le pieces adjacent the junction between e saturated Yttgili? rtion and the unsaturated remainder 0 t8; pole .face, a main workcircuit ener said main brushes, and means or excit' said salient pole pieces comprising a fi e ld winding energized from said auxiliary I brush and the main brush. adjacent to saidsaturated trailing portion, and .a buckixig series 'windin energized in accordance wi the main l'oa current.

lar machine, it is obthe pole piecesadjacent' the junction O0 'lo modifications thereof will :be evident to those skilled in the art and accordingly I do not wish to belimited to the exact ar- 15 modifications which may come withinthe In testimony whereof, -I':have .hereunto1 -f subscribed my name this 14th day of My, connected in series with the main 'exclting" 1928," v, v I: 

